The Body of Evidence for Advanced Technology in Radiation Oncology

Extract

Proton therapy has struck a nerve in the national dialogue about cancer comparative effectiveness research in the United States. Unlike photon-based radiotherapy, proton therapy delivers radiation within a finite range, depositing dose in a tumor target with essentially no residual radiation beyond the tumor. Proton therapy radiation dose distributions often appear superior to photon-based treatments like intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy, particularly in the reduction of low and intermediate radiation dose to normal tissues.

However, proton therapy has greater intrinsic uncertainties than photon-based treatments, both biological and physical. For example, uncertainty exists about where the finite range of protons terminates in tissue; to compensate, proton treatment centers routinely overshoot tumor targets to ensure adequate radiation coverage ( 1 ). Proton therapy uncertainties and methods by which such uncertainties are mitigated could impact important clinical outcomes. Thus, the comparative effectiveness test for proton therapy is whether it leads to incremental reductions in morbidity or improvements in survival and disease control, not whether the dose distribution looks better or mechanism of radiation delivery is novel ( 2 ).